1. Field of the Invention
This invention relates to a metalworking composition having lubricating and cleaning properties and a method for preparing the same. More particularly, the invention relates to water-based lubricants containing non-hazardous components for use as metalworking fluids.
2. Description of the Prior Art
The prior art has proposed numerous water-based metalworking fluids intended for use where a lubricant is required to be in contact with a metal surface as it is worked mechanically. For such machining operations as metal cutting, milling, grinding and the like, it has been proposed to use metalworking fluids in the form of water-containing emulsions based on mineral products and additives to improve lubrication, as more fully described in U.S. Pat. Nos. 3,249,538 and 3,933,658. While these water-in-mineral oil, emulsion-type metalworking fluids are generally economical to produce, the mineral oil component of these fluids produce oil smoke and mist at elevated temperatures to create environmentally unsafe conditions for the worker. Moreover, mineral oils also form certain polyaromatic hydrocarbons which have been recently recognized as being carcinogenic substances.
In recent years increased concern for industrial safety has created environmental control legislation in the United States which imposes strict requirements on the type of metalworking fluids that may be used in the industry. To fulfill the requirements of the fluids from environmental aspects, the metalworking art has reverted to the use of fatty oils, i.e. vegetable and animal oils and fats, which were used extensively as suitable raw materials for lubricants before the cheaper mineral oils came to dominate the market. Fatty oils can be completely broken down biologically and do not present the health and environmental problems associated with mineral oils.
A metalworking emulsion of the oil-in-water type based on triglyceride oils is disclosed in U.S. Pat. No. 4,237,021. The emulsifying agent used consists of fatty acid monoglycerides and alkali soaps of fatty acids. To increase the lubricating properties of the disclosed emulsions, it is generally necessary to add fatty acids and an alkanolamine or fatty amine. However, because of the acidic properties of fatty acids, undesirable problems appear. It has been found that early sludge is often formed and certain metal alloy bearing surfaces are readily corroded by oxidation and polymerization when employing emulsions of this type.
It is accordingly a primary object of the present invention to provide an improved metalworking composition in the form of an oil-in-water emulsion having excellent lubricating properties and comprising essentially harmless components from environmental and health aspects.
It is a further object of the invention to provide a method for preparing homogenized metalworking emulsions of the oil-in-water type which are sufficiently stable on storage and capable of maintaining their viscosities under variable conditions.
It is among the additional objects of the present invention to provide water-containing metalworking compositions which have good heat resistance and relatively good cooling and cleaning properties, which do not require the addition of numerous additives, can be readily disposed of when spent to facilitate convenient waste treatment, can be easily applied to form an adhering film on the surface of a metallic workpiece, and which prevent problems associated with acidic impurities such as corrosion, oxidation and polymerization.
Other objects and advantages of the present invention will become apparent from the following general description.